When something is fastened on sheets, such as a clothing material, the needle of a safety pin or a pin is typically stuck into the material. This needle must damage the material, even if it is a small amount of damage. For example, if a name plate is fastened with a safety pin on the same position of the clothing everyday, the pin hole will become bigger very quickly. In the case of a delicate material, such as silk, even if it is not repeatedly stuck, when just one sticking needle might make a very tiny hole, it spoils the worth of clothing.
In order to solve this problem, the present inventors disclosed “fastening tools” in the following 2 inventions.
JP.A2006-230728
JP.U2007-2484
These inventions provide fastening tools which fasten nameplates or on clothes without sticking needles. These fasteners have utility because they achieve “easy fit and less drop-out” which was not achieved by the badge type prior art. Also, these tools do not press on clothes hard and therefore prevent damage to the materials.
However, the holding performance of these tools depends on the resiliency of the springs. Therefore, when the force against resiliency of the spring is set, the fastening tool may drop out. If the spring was stronger to prevent drop-out, not only would the advantage “easy fit” be lost, but a fear that the tool presses on the material too strongly might appear.
A certain size of the fastening tool is required to obtain a length for the spring's expansion and then this length makes sufficient fastening performance. Therefore the minimum sizing of a tool is limited. The shape of the tool has to be slender so a spring could expand and contract therein. The prior arts, such as a safety pin, are applied in many fields because these prior arts can be made in very small sizes. Compared with the prior arts, the abovementioned fastening tools have too many size limitations.